Richards announced his retirement last month.
He wrote for BBC Sport: "I am a pundit now, not a player, but when I was getting abused by Villa fans on Twitter and Instagram, I was still battling to save my career.
"Deep down, I probably knew it was already over, but for most of the two and a half years between my 295th and final game as a professional, against Wolves in October 2016, and the day I announced my retirement in July this year, I was living in denial.
"I would keep on waiting for each new manager to come in at Villa and say to me 'I'll give you a chance', but it got to a stage where that could never happen, because although I could train 100%, I was never able to play.
"I could run and I could jump - but I couldn't twist on my right knee, and it would not get any better. Whatever I tried, it did not make any difference."